Conventional laundry detergent formulations usually contain surfactants, builders and other additives to improve the removal of soil. It is recognized by those skilled in the art of formulating detergents that enzymes, a unique class of proteins, can be added to conventional laundry detergents to improve the cleaning of textiles. Enzymes are substances formed by living cells which catalyze biochemical reactions, and when used in detergent formulations, they enhance the cleaning ability of laundry detergents. Likewise, it is also known to those skilled in the art that when conventional enzyme-containing laundry detergents are used in the wash process, the surfactant and builder present in the formulation enhance the action of the enzyme. Common enzymes included in conventional laundry detergents include: amylase, which breaks down starch; protease, which catalyzes reactions that break down proteins; lipases which work on lipids; and cellulase which breaks down cellulose.
Cellulases are known in the art as enzymes that hydrolyze cellulose (.beta.-1,4-glucan linkages) to form glucose, cellobiose, cellooligosaccharides, etc. Celluloytic enzymes are recognized by those skilled in the art of detergent formulation not only as agents that enhance the cleaning ability of detergents but also as agents that soften and improve the feel of cotton. Repeated washing of cotton-containing fabric can result in the fabric assuming a harsh and unpleasant stiffness. The use of laundry detergent formulations containing cellulase can reduce or eliminate the stiffness and harshness of fabrics which contain cotton. In addition cellulase enzymes also assist in maintaining the whiteness of fabrics and can play a role in maintaining colors. Moreover, cellulase enzymes in laundry detergent compositions are employed as stain removers and contribute to the overall impression of cleaning performance perceived by the consumer.
However, it is recognized by those skilled in the art of detergent enzymology that cellulase preparations are complex mixtures of which only a certain fraction is effective as a catalyst in the washing process. For example, the complete fungal cellulase enzyme is composed of multiple components which include exo-cellobiohydrolases, endoglucanases and .beta.-glucosidases. It can be difficult to optimize the production of multiple enzyme systems since the cost of producing an enzyme which is comprised of a complex mixture can be prohibitive. Fortunately, it is now known that cellulase preparations useful to enhance the cleaning ability of detergents, and to soften and improve the feel of cotton, comprise the above-mentioned endoglucanase component which possesses a high ability to bind and degrade cellulose. Moreover, cellulase preparations comprising a large amount of endoglucanase component are less costly to produce than complex mixtures of enzymes and can be used in smaller quantities to produce the desired cellulase cleaning and softening effects.
It is well known to those skilled in the art of enzymology, that the cellulase enzyme can contain a region that functions primarily to bind the cellulase enzyme to the cellulose substrate. Cellulases that contain this domain are identified as surface-active cellulases since they possess the ability to bind to the surface of textiles. Cellulases lacking this domain are designated as nonsurface-active cellulases since they cannot bind with the cellulose contained in textiles for any considerable length of time. The discovery of a particular combination of endoglucanases capable of enhancing cleaning and improving softening would permit the cost-effective production-of cellulase using recombinant deoxyribonucleic acid (DNA) methods.
It is further well known in the art that certain cellulases can produce negative effects on cotton garments, such as weight loss and tensile strength loss. These negative effects can be minimized by choosing a combination of surface-active and nonsurface active cellulases which results in an optimum length of contact with the garment. Similarly, these negative effects can be minimized by controlling the length of time the enzyme is active in the wash liquor.
Accordingly, despite the aforementioned disclosures in the art, the need exists for a detergent composition containing an enzymatic mixture comprising a specific combination surface-active and nonsurface-active endoglucanases which enhances the cleaning ability of laundry detergents and which softens and improves the feel of cotton. There is also a need for such a detergent composition which maintains colors and removes stains. Furthermore, despite the previously mentioned disclosures in the art, there still remains a need for such a detergent composition comprising a specific combination of surface-active and nonsurface-active cellulases that is capable of delivering enhanced cleaning, softening and color maintenance results without concomitant weight loss and tensile strength loss in cotton garments.